1. Yuki D. Takahashi University of California, Berkeley 2002 / 9
Cooperation Between Lunar Scientists and Astronomers: Proposing Lunar Science Missions to Enable Astronomy from the Moon
Yuki D. Takahashi
University of California, Berkeley
2002 / 9

2. Why Astronomy from the Moon?
Some observations are feasible only by using the Moon...
as a Shield (against Sun / Earth)
Permanent darkness
Radio quietness
as a Platform (stable & large area)
Interferometry w/ long baselines
for Access
Serviceability, Expandability
Human access from a lunar base
Much lower risk
Examples:
Very-low-frequency (VLF) radio array
Infrared telescope(s) for ES planets [

3. Why Very-Low-Frequency astronomy?
[pictures from gsfc.nasa.gov]
Discover the New Universe (< 30 MHz)
The only unexplored part of the electromagnetic spectrum in astronomy
Revolution in human view of the Universe through unexpected discoveries
Relies on the Moon:
Interference shielding crucial (see ->)
Stable platform for many array elements
Urgent! (before Moon is contaminated)
[Desch 1990]

4. Lunar Far Side VLF Array
Site: a large far side crater (Tsiolkovsky ~100km)
Array of many short crossed dipole antennas
All-sky aperture synthesis mapping
Relay sat. at L2
Require:
Far side access
Funding > $1B
Phase III (~2030)
[ESA]
25 cm
2 m

5. Current Status Technically feasible w/ current technology.
Over 40 articles/papers since the 1960s.
At least 3 major published design studies:
1992 Hughes Aircraft Company.
1993 International Space University design project.
1997 ESA design study.
No funding/plan.
Must publicize the significant discovery potentials of very-low-frequency astronomy.
Must begin with a cheap mission for an initial survey.

6. New Realistic Proposal
To save cost: Piggyback on a lunar lander mission.
Antennas themselves are very light-weight.
Share power/communication systems w/ the main mission.
Antennas deposited by existing rovers.
An ideal technology demonstration task?
Inexpensive addition to any mission’s scientific potential.
Next landers: Lunar South Polar region.
Water ice, Lunar base
Malapert Mountain (communication, power)
Initial survey of the unknown sky:
To discover new objects / phenomena at very low frequencies.

7. Lunar South Polar Site Malapert Mountain (5 km high)
could shield terrestrial interference for an observatory situated on the opposite side of it from Earth.
Linear array will work
Rotation synthesis
Simple deployment
Sky coverage
limited, but sufficient
for an initial survey.
Accessibility
From the lunar base
for future expansion.
[Margot et al. 1999]

8. To Make It Happen Reconfirm the need for the lunar environment.
Identify an ideal site near the lunar south pole.
Propose an affordable piggyback mission.
We need:
- Confirming measurements on the Moon.
- Detailed survey of the candidate sites.

9. * Lunar “Ionosphere”? Sets the lowest observable frequency. Available:
(10~30 MHz on Earth)
Available:
Only day-time
measurements from
the 1970s (Apollo
CPLEE / SIDE, Luna 22)
Need:
Cut-off frequency at the polar region.
Variations (day/night/transitions)
[Dual-frequency phase-lag measurements.]
[Benson et al. 1975]

10. * Radio Quietness Reconfirm the lunar advantage. Sets the sensitivity.
Available:
RAE-2 demo
of terrestrial noise at
the Moon ->
Need:
Interference level
in the polar regions.
Shielding by a mountain (Malapert).
[Low frequency receivers on site: 50 kHz – 30 MHz]
[Alexander et al. 1975]

11. * Terrain/Topography Find an ideal site (flat, smooth, large)
Transportation, deployment, line-of-sight communication
Available (Clementine):
Camera: Dx = 30 m
Altimeter: Dz = 40 m
Need:
High-resolution
topography of the
south polar regions
(especially dark areas)
Dz = ½ m, Dx = 10 m
[Clementine (NASA)]

12. * Subsurface
Ensure no disturbing reflections of radio waves off of subsurface structures.
Site selection.
Available:
Apollo Lunar
Sounder Exp.
Need:
Radar sounding
at 50 kHz - 30 MHz.
To ~10 km depth.
[Lunar Sourcebook 1991]

13. Other measurements Magnetic field at candidate sites (confirm low)
Thermal environment
Accessibility (deployability)
Malapert Mountain utility
Seismicity

14. Upcoming Missions LunarSat / SMART-1 SELENE (2006)
Images of the south polar region.
SELENE (2006)
Lunar Radar Sounder (4-6 MHz)
Subsurface reflections down to ~ 5 km (Dz=100m)
Radio interference from Earth / Sun.
Terrain Camera & Laser Altimeter (Dx=10m, Dz=5m)
Radio Science (lunar “ionosphere”)
Lunar Magnetometer

15. Remaining Measurements
The most crucial measurements to be planned:
Topography at vertical resolution Dz = ½ m, with spot size Dx = 10 m.
In-situ measurements with dipole receivers:
Plasma cut-off frequency
Interference levels
Observation test

16. Summary
The unique lunar environment enable astronomical observations that would otherwise be impractical from Earth or free space. The unknown, very-low-frequency window is especially promising for significant discoveries.
VLF interferometer could be deployed very inexpensively as a piggyback project on a larger lunar lander mission.
To propose such a mission, we need a more detailed in-situ survey of the conditions at the candidate sites.
We should keep these interests in mind as we plan lunar science missions to make the most out of them. Thanks!
Acknowledgements:
I’d like to thank the individuals of NASA's Human Exploration and Development in Space (HEDS) Enterprise for supporting and inspiring students like me.

17. Aim
Who: NASA, lunar/planetary scientists, SELENE, SMART-1, Mike, Bernard
Get them interested in astronomy from the Moon.
Motivation
Inexpensive mission proposal
Ensure they know what measurements are demanded and why important.
Existing data
Required measurements